Latent image printing device

ABSTRACT

A LATENT IMAGE PRINTING DEVICE COMPRISING A SUBSTRATE, A FIRST LAYER OF ABRASIVE MATERIAL, AND A SECOND LAYER OF NON-ABRASIVE MATERIAL PLACED AS A NEGATIVE FACSIMILE OF THE IMAGE TO BE PRINTED UPON SAID FIRST LAYER, SAID LAYERS MATCHED FOR SIMILARITY OF PROPERTIES OF COLOR, GLOSS AND FLUORESCENCE, TO RENDER THE IMAGE UNDETECTABLE UNDER NORMAL OR ULTRAVIOLET LIGHT. THE IMAGE IS DEVELOPED BY RUBBING, FOR EXAMPLE, A METAL OBJECT OVER THE SURFACE OF SAID SUBSTRATE, CAUSING ABRADING OF THE OBJECT IN THE ABRASIVE AREAS AND &#34;PRINTING&#34; OF SAID IMAGE.

United States Patent O 3,567,482 LATENT IMAGE PRINTING DEVICE Harry 0.George, Belle Mead, and James F. Martone, Somerville, N.J., assignors toInternational Business Machines Corporation, Armonk, N.Y. No Drawing.Filed Jan. 12, 1968, Ser. No. 697,296 Int. Cl. B44f 1/10 U.S. Cl. 1171.72 Claims ABSTRACT OF THE DISCLOSURE A latent image printing devicecomprising a substrate, a first layer of abrasive material, and a secondlayer of non-abrasive material placed as a negative facsimile of theimage to be printed upon said first layer, said layers matched forsimilarity of properties of color, gloss and fluorescence, to render theimage undetectable under normal or ultraviolet light. The image isdeveloped by rubbing, for example, a metal object over the surface ofsaid substrate, causing abrading of the object in the abrasive areas andprinting of said image.

FIELD OF THE INVENTION Devices, composition and structure, having aconcealed message, image, or printing thereon, normally not detectableuntil said message, image, or printing is developed by rubbing, peeling,or mechanically working the surface of said device.

BACKGROUND OF THE INVENTION In recent years, to induce customers topatronize their places of business, many commercial firms such assupermarkets, gasoline service stations, etc., have instituted games tolure customers. One of the more usual methods employed in these games isto give the customer a coupon each time the customer patronizes thebusiness establishment. The coupon has a concealed message which isrevealed when the customer removes the covering layer, such as byholding the coupon under water, under heat, or light. The message willusually be one part of many needed to complete the game, with cashprizes or awards being given for a customer who gets the requisitenumber of component parts. The prizes often range in the thousands ofdollars value.

To maintain fairness to customers and to prevent fraud upon thecompanies issuing the games, it is necessary that the messages beconcealed in such a manner as to assure the random distribution of thesegame coupons to customers. Further, it is necessary to assure that thecoupons cannot be tampered with, so as to allow one to perpetrate afraud upon the issuing company, such as by raising the amount of moneyon a coupon, or by changing the message on a coupon so as to completeone of the games to receive a higher cash award than would have beenreceived, if any would have been received at all. Further, thesecoupons, being issued by so many gasoline service stations,supermarkets, etc., total millions of coupons annually distributed.Thus, the cost of the coupons must be kept at a minimal price, whilestill insuring both the random distribution and protection from fraud.

Ideally, it should be possible for a customer upon receipt of such acoupon to immediately be able to ascertain what the hidden message is,so that he may be able to ascertain immediately whether he has wonsomething. Further, the customer should be able to do this with aminimum of inconvenience, which is not attendant those coupons currentlyrequiring exposure to heat, light, or the use of a fluid, such as water,to expose the message.

Above all, no matter what method is used, it must not ice only beconvenient and tamper proof, but must so protect the hidden messagethat, prior to development, it cannot be detected by such means as lightreflection or by fluorescence under ultraviolet light.

SUMMARY OF THE INVENTION It is an object of this invention to preventtampering with such game coupons by providing a coupon whose messagecannot be revealed by normal light or by fluorescent radiation means.

Another object is to preserve the fairness of distribution of suchcoupons by providing a coupon whose message cannot be ascertainedwithout destroying the coupon.

Still another object of this invention is to allow high speed commercialproduction of these game coupons by utilizing a structure adaptable tomanufacture by high speed printing machines.

Another object is to allow high speed commercial production of suchcoupons by utilizing ink compositions suitable for gravure printing.

The problems of the prior art are overcome by the structure andcomposition of the present invention. Briefly stated, this inventioncomprises a latent image printing device comprising a substrate, a layerof abrasive material, and a layer of non-abrasive material, the image tobe printed comprised of surface responsive areas of abrasive material.The layers are matched for similar properties of color, gloss, andfluorescence, to render the image undetectable under reflected light orultraviolet light. As used herein, the word similar, as applied toproperties, means sufiiciently matched to obtain the desired result ofan image which is undetectable under normal or ultraviolet light. Theimage is developed by rubbing, for example, a key over the surface ofthe substrate, causing abrading of the key by the abrasive material, andthus printing of the latent or hidden image by particle capture at theabrasive areas from abrasion of the key. The layers above can be printedupon, for example, a paper substrate by the used of certain gravureinks, the gravure printing method being a high speed and accurateprinting method. While the above is a description of one structure ofthis invention a better understanding of the invention may be had byreference to the general description of this specification.

GENERAL DESCRIPTION This invention utilizes the relationship as to theproperties of color, gloss, and fluorescence of adjacent layers of amutlilayer structure to prevent the detection by reflected light or byfluorescence of the printing, or hidden message, contained within thelayers. For the purposes of this invention, the term latent image willbe used to connotate the message or image contained within the layers,and to be revealed by appropriate means, to be described later.

One form of the invention utilizes an abrasive ink to print a message ordesign upon a substrate capable of receiving the ink. The abrasivematerial, or ink, is thus placed upon the substrate. Over this and overthe surrounding area, which may include the entire substrate surface, isapplied a thin layer of a clear, hard, brittle resin. Such a resin maycontain, for example, zinc stearate. If the abrasive material and thenonabrasive material, here the hard brittle resin, are matched in theproperties of color, gloss, and fluorescence, the over layer of theresin will render the abrasive ink invisible, but does not render itnon-abrasive to a metal object that may be rubbed over the printed area.

The abrasive material may be, for example, substantially one part byweight Super Floss Celite Mineral Filler, a product of Johns-ManvilleCorporation, which is a diatomaceous earth; 12 /2 parts by weightmethanol or denatured alcohol; and parts by weight Vinac 5-5-50, aproduct of Air Reduction Company, a 50% solution of polyvinyl acetate inmethanol. The non-abrasive material, in the form of a non-abrasive ink,may be substantially 1 part by weight of zinc stearate, parts by weightof Dow Resin PS-2 (a product of Dow Chemical Corporation), a lowviscosity polystyrene, and 60 parts by weight of toluene. The totalviscosity of the non-abrasive material should be less than secondsviscosity using a No. 2 Zahn Cup test.

The above inks may be applied by gravure printing techniques.

In the above formula the Celite mineral filler is the abrasive, thoughit is by no means the only abrasive that could serve the purpose. TheVinac 5-5-50 material serves as an adhesive to hold the abrasiveparticles in place. Other adhesives could be substituted in the formulawith similar results. The zinc stearate is used as the lubricant so thatthe printed paper can be rubbed with a metal object with greater easeand with less tendency to disrupt the surface of the paper. Otherlubricants may be substituted for the zinc stearate with similarresults. The polystyrene resin gives the entire area to which it isapplied a similar appearance, making the message printed with abrasiveink invisible until developed by rubbing with, for example, a metalobject. Though the polystyrene is left as a film over the abrasive ink,it is such a hard, thin and brittle film that it does not prevent theabrasive ink from acting on the metal object. Thus, as the metal objectis rubbed across the image, the polystyrene film will crack or chip,exposing the abrasive material, causing the abrasive to abrade part ofthe metal. The abraded particles are captured by the abrasive material,leaving a visible image behind. Thus, the latent image is developed, orprinted.

In most applications it is desirable to print over the latent image alight pattern or scroll using colored ink. This scroll is simila to thatwhich appears on safety check paper. This scroll not only has adecorative effect but also makes it more difficult to see the latentimage before it is developed. It also makes it more difficult to makeany alterations to the latent image without defacing the document. Wehave found that the colored gravure inks which are used to print thesescrolls are made extremely sensitive to erasure if a metallic soap suchas zinc stearate is blended into the gravure ink. While safety gravureinks are most sensitive to erasure when treated in this manner, we havebeen able to molify even the socalled permanent inks to make them verysensitive to erasure.

Thus, the above structure comprises a substrate, an abrasive layer inthe form of the image to be printed, and a non-abrasive layerovercoating the entire area of the abrasive layer. The two layers,chosen to be similar in the properties of color, gloss, andfluorescence, renders the latent image undetectable by reflection or byfluorescence. For further protection, printed scroll work may be placedupon the final layer.

It is important to keep in mind that this invention relates to theprinting of images which cannot be detected when examined under normalor even ultraviolet light, but which can be made distinct by rubbing theprinted surface with a metal object such as the edge of a key. Singleapplication of abrasive ink would provide an image that can be developedby rubbing with the key, but such an image would be visible due todifferences in light reflection, color, or fluorescence of the inks inthe paper, or substrate. To make the latent image non-visible untilrubbed with metal, or other abradable objects, we have developedcombinations of abrasive and of non-abrasive materials or inks whichhave similar properties of color, gloss, and fluorescence. These inkscan be used to form structures achieving the objects of this inventionin different ways. Thus, for (xample, the abrasive ink can be laid downin a solid area Without design and the non-abrasive ink can be printedover it in a negative facsimile of the desired image to be printed,forming a protective surface in selected areas which are not to bedeveloped with a metal object.

Another way is to print the non-abrasive ink over the substrate toprovide a background with suitable color and gloss on which to apply theabrasive ink, which would be applied in the form of a positivefacsimile, or the positive image, which is to be made visible by rubbingwith the metal object.

Further, a substrate could be made having an abrasive materialincorporated therein, where the abrasive material forms at least a partof at least one surface of the substrate. A layer of non-abrasivematerial may then be placed upon this abrasive layer in a negativefacsimile of the image to be printed. Again, as before, it is importantthat the non-abrasive material be chosen similar in the properties ofcolor, gloss, and fluorescence, to the background of the substrate inthis case. Conversely, a substrate may be utilized having at least onesurface being substantially non-abrasive, and then placing the layer ofabrasive material upon the surface in the positive facsimile or image ofthat to be printed, and matching the abrasive material in the propertiesof color, gloss, and fluorescence to the non-abrasive surface.

In all of the above, it is realized that every material, to some extentat least, can be considered as abrasive. The important feature to keepin mind is that an area chosen to be abrasive, or more abrasive, inrelation to its adjacent area, Will cause a greater amount of abradingin that area. Thus, even if two abrasive areas were placed next to eachother, the more abrasive area would cause a greater amount of abrading,or a greater amount of deposition or capture of abraded material in thatarea, rendering, at the very least, a contrast between the two areas,rendering the latent image visible.

Where a non-abrasive layer overlays an abrasive area, no printing willoccur, except in that example wherein a chippable surface layer isdeposited over the abrasive layer. Those abrasive areas which representthe image to be printed may thus be called the surface responsiveabrasive material areas; that is, those areas that will respond todevelopment with an abradable object by abrading said object.

Thus, the above illustrations may be summarized in brief by describingthem as a latent image device comprising a substrate having at least oneof its surfaces comprised thereon of abrasive material and non-abrasivematerial, the image to be printed comprised of surface responsive areasof said abrasive material, the abrasive and non-abrasive materials beingchosen to be similar in the properties of color, gloss, andfluorescence.

The abrasive material, such as in ink form, can be made abrasive byincorporating pigments such as diatomaceous earth or other forms ofsilica, titanium dioxide, clay, talc or calcium carbonate into asuitable vehicle. The non-abrasive material, such as in ink form, can beprepared by incorporating metallic soap, finely divided resins, orfinely divided starch, flour, or other organic substances into avehicle. It can even be prepared with soft, finely divided inorganicmaterials as long as they are substantially less abrasive,,but similarin color, gloss, and fluorescence, to the pigments used in the abrasiveink.

While our experiments have been mostly with gravure inks, the sameprinciple may be applied to letterpress, lithographic and flexographicinks, and other methods of application of an abrasive and non-abrasivematerial to a suitable substrate.

An example of a combination of inks suitable for application on a r'ravure press is as follows: the abrasive ink comprises substantially 5parts titanium dioxide, 5 parts vinyl aretate, and 15 parts methanol;and the nonabrasive ink comprises substantially 1 part zinc stearate, 5parts vinyl acetate, and 15 parts methanol. If, as applied on the press,these two inks are not a perfect match, they can be made to match by aslight increase or decrease in the amount of zinc stearate in thenon-abrasive ink.

The latent image devices of this invention, as utilized in, for example,game coupons, thus meet the objects of this invention. The latent imagecannot be detected under normal or ultraviolet light, due to thematching of properties of the layers in color, gloss, and fluorescence.Tampering with the surface of such coupons, due to the abrasive natureof the abrasive ink, will cause the image to be revealed, and thusexpose such tampering. Changing the printed image by additions ofadditional abrasive ink in a given manner, or covering a portion of theabrasive ink with a non-abrasive material, is easily revealed due todifferences between the materials used in attempting to change thelatent image by reflection under normal light or by fluorescence underultraviolet light, unless a perfect match of inks is achieved, which isnot likely in the common situation of fraud.

The structures of this invention are clearly applicable for use on highspeed printing presses, such as gravure presses, for which specific inkcompositions are disclosed. Further, if a final overlayer of scrollprinting with a colored tamper-proof type ink is utilized, theunderlying image is made further undetectable, and the card madevirtually tamper proof.

It should be noted that while gravure printing is generally done uponpaper, and this disclosure has been described predominantly withreference to a paper substrate, other substrates, such as certainplastics or plastic-impregnated papers, may also be used, as well as anyother substrate that may be adapted for this purpose. It is onlynecessary, of course, that the inks or materials utilized adhere to thesubstrate, and do not undergo such chemical reactions as to change theirproperties in any substantial manner.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A latent image printing device comprising:

a substrate having at least one of its surfaces comprised of abrasivematerial in the positive image of the image to be printed, and a layerof hard, brittle non-abrasive material overlying said surface of saidsubstrate, said abrasive material and said non-abrasive material beingsimilar in the properties of color, gloss and fluorescence, so as tocause said image to be printed to be rendered undetectable by lightreflection or by fluorescence,

whereby by rubbing said surface with an abradable object saidnon-abrasive material chips Off from and exposes said underlyingabrasive material layer, said image being printed by particle capturefrom abrasion of said abradable object.

2. In a latent image printing device comprising a substrate having atleast one of its surfaces comprised of abrasive material in the positiveimage of the image to be printed, and a layer of hard, brittlenon-abrasive material overlying said surface of said substrate, saidabrasive material and said non-abrasive material being similar in theproperties of color, gloss and fluorescence, so as to cause said imageto be printed to be rendered undetectable by light reflection or byfluorescence, wherein said materials in the form of inks are placed uponthe surface of said substrate as successive layers by gravure printingmeans, the combination of inks comprising:

an abrasive ink comprising substantially one part by weight ofdiatomaceous earth, 12 /2 parts by weight methanol, and 10 parts byweight of a solution of polyvinyl acetate in methanol; and

a non-abrasive ink comprising substantially one part by weight zincstearate, 20 parts by weight of polystyrene resin, and parts by weightof toluene.

References Cited UNITED STATES PATENTS 696,633 4/1902 Hall 1171.7730,823 6/1903 Hall 1l71.7 3,001,886 9/1961 Shrewsbury et al 117-1 OTHERREFERENCES Dino Dollars, May 8, 1967, 283-6.

MURRAY KATZ, Primary Examiner US. Cl. X.R. 117-45; 2836

